Anthropic Sandbox Runtime vs microsandbox

Anthropic Sandbox Runtime (srt) is a free, open-source research preview that applies filesystem and network restrictions to processes at the operating-system level, without requiring a container. It can be used as a CLI tool or library to sandbox agents, local MCP servers, bash commands and other processes. Filesystem writes and network access are denied by default, with configuration options to allow paths and domains. The project documents macOS, Linux and Windows support, using sandbox-exec, bubblewrap or a dedicated local sandbox account with Windows Filtering Platform and filesystem ACLs, respectively. Windows is marked alpha. Install it from npm with `npm install -g @anthropic-ai/sandbox-runtime`. Linux requires bubblewrap, socat and ripgrep; macOS requires ripgrep, and Windows needs a one-time elevated setup step. On macOS, srt can provide real-time alerts from the system sandbox violation log. Linux bubblewrap has no built-in violation reporting, and Linux network filtering relies on proxy environment variables, which some programs may ignore. The preview is developed for Claude Code; its APIs and configuration formats may evolve.

Microsandbox runs untrusted workloads inside microVMs, each with its own Linux kernel, filesystem, and network boundary rather than sharing the host kernel. It can run AI agents, user code, plugins, CI jobs, scrapers, and automation. The local runtime starts on a user's machine without a daemon, root service, or account; it can also run on personal servers or clusters, and its cloud platform can be deployed in the user's infrastructure. Microsandbox offers SDKs for TypeScript, Rust, Python, Go, and Ruby, plus a CLI and MCP workflows, and accepts OCI images from container registries. By default, sandboxes can reach the public internet, while private, host-local, link-local, and metadata destinations are blocked; egress can be allowlisted or disabled. The runtime is open source under Apache 2.0. The Free plan is $0 per month, while paid plans start at $49 per month. Microsandbox Cloud is in private beta and requires an access request.